a. 太阳的, 靠近太阳的

[ adj ]
pertaining to or near the sun; especially the first rising of a star after and last setting before its invisibility owing to its conjunction with the sun
<adj.pert>
the heliacal rising of the Dog Starthe heliacal or Sothic year is determined by the heliacal rising of Sothis (the Egyptian name for the Dog Star)

Heliacal \He*li"a*cal\, a. [Gr. ? belonging to the sun, fr. ?
the sun: cf. F. h['e]liaque.] (Astron.)
Emerging from the light of the sun, or passing into it;
rising or setting at the same, or nearly the same, time as
the sun. --Sir T. Browne.

Note: The heliacal rising of a star is when, after being in
conjunction with the sun, and invisible, it emerges
from the light so as to be visible in the morning
before sunrising. On the contrary, the heliacal setting
of a star is when the sun approaches conjunction so
near as to render the star invisible.